Compressed sponge animals are known to be contained within a thin, water soluble capsule. The capsule is usually placed into warm water, where it reacts with the water to completely dissolve. After the capsule dissolves, water contacts the sponge and causes the sponge to expand.
An example of such a capsule is disclosed in U.S. Pat. No. 3,680,250 to Hetrick. In this patent, a fishing lure is housed within a water-soluble capsule. When the lure is to be used, the capsule is immersed in water, the capsule dissolves, and the lure is released.
In U.S. Pat. No. 4,481,326 to Sonenstein, a water soluble film of polyvinyl alcohol and polyvinyl pyrrolidone is disclosed. This patent teaches use of films which are rapidly soluble in cold and warm water and are formed from blends of water soluble polyvinyl alcohol (partially hydrolyzed polyvinyl acetate) and polyvinyl pyrrolidone. These polymers are compatible and form homogeneous mixtures from which clear, transparent, non-tacky, easily handlable, mechanically strong films can be formed.
In U.S. Pat. No. 3,091,053 to Growald, a foamable resin and catalyst in an inactivated or unfoamed state is located in a collapsed envelope located within two halves of a releasable shell. Upon application of heat to the shell, the critical temperature of the foamable plastic is reached, and a rapid volumetric expansion takes place within the plastic envelope which is shaped in the form of an animal. A joint formed between the two halves of the shell fails, thus releasing the filled envelope in the shape of an animal from within the shell through the separated shell joint.